This Physician Scientist Award proposal is designed to permit the candidate to acquire basic and advanced knowledge and skills in molecular biologic investigation and to apply these to the study of cartilage diseases. Graduate coursework in cell and molecular biology and protein biochemistry which provide a firm basis for future research endeavors will be taken during the first year of this Award. During Phase I, transgenic mouse models of human disease, containing mutations in the alpha2 chain of type IX collagen, will be generated. Type IX collagen Is a cartilage-specific molecule with unique structural features that likely render the molecule necessary for normal cartilage structure and function. Because mutations in type II collagen have been shown to cause human disease, it is quite likely that abnormalities of type IX collagen do also. Three or four mutations in the alpha2 (IX) chain, which contains interchain disulfide bridges, crosslink sites to type II collagen, a glycosaminoglycan attachment site and a kink region, will be constructed and transgenic mice containing these mutations generated. Abnormal phenotypes will be characterized radiographically and microscopically. During Phase II, mechanisms by which these mutations alter normal development, structure and function of cartilage will be sought. At the same time, information on the structure-function relationship of various domains of the type IX molecule will be obtained. This phase of the Award will prepare the candidate for additional studies of the molecular genetics of human cartilage diseases.